1. Field of the Invention
The present invention relates to a feed nozzle unit disposed between a tundish nozzle and a mold in a horizontal continuous casting device, and more particularly to a unit in which assembly is simplified and resistance is increased against thermal and mechanical shock applied thereto during a continuous casting process.
2. Description of the Prior Art
FIG. 1 shows a longitudinal sectional view illustrating a principal part of a horizontal casting device as an example of the prior art. The casting device comprises a feed nozzle 1, a connecting refractory material 2 and a mold 3, connected in coaxial relation. The feed nozzle 1 is connected to a tundish nozzle 4 and molten metal M is transferred towards the mold 3, water flows through a water-cooling jacket 6 so as to cool the mold 3, and molten metal is solidified from outside and drawn intermittently to the arrow A direction so as to thereby perform continuous casting. In the figure, reference numeral 7 designates a feed nozzle assembly member and numeral 8 a fixing tool.
In such casting device, the feed nozzle 1 in itself is restricted in position by the assembling member 7 and fixed in coaxial relation with the mold 3 as shown in the figure. However, since the connecting refractory material 2 is only grasped between end surfaces of the feed nozzle 1 and the mold 3, centering of the refractory material 2 is considerably troublesome and difficult. Moreover no support member exists outside of the connecting refractory material 2 and therefore the refractory material 2 is liable to be broken by thermal shock or external mechanical force produced during the continuous casting process. As a result, molten metal penetrates the broken position and a fin is produced on the outer surface of a continuously cast strand (c.c. strand) such that the inner surface of the mold 3 may be damaged.
In order to eliminate the above-mentioned disadvantages, for example, a method as shown in FIG. 2 (being a longitudinal sectional view of a principal part) has been proposed. In the figure, taper machining is performed at connecting portions of the connecting refractory material 2 and the mold 3, respectively, but centering is not always easy to accomplish. Further, in order to prevent penetration of molten metal between the connecting refractory material and the mold, the tightening force between both members may be increased. However, if the tightening is performed excessively or without uniformity, breakage of the connecting refractory material 2 may be accelerated. The mold 3 and the feed nozzle 1 are tightened and fixed respectively by the assembling member 7 and the fixing tool 8 as above described. The tightening force, which attains a maximum value of 4000 kg, directly acts on the taper machining portion of the connecting refractory material 2 and compresses the refractory material 2 to decrease the diameter. The compressive force, which is uniform and suitable, acts to eliminate tension strain at the interior of the connecting refractory material produced during the casting and therefore is effective. However, uniform tightening is difficult in practical use and therefore local stres may be produced at the interior of the refractory material which may thus be broken.
In the connecting refractory material which is weak in resistance against thermal shock, a method as shown in FIG. 3 (being a longitudinal sectional view of a principal part) has been proposed. In this method, a reinforcing ring 9 is installed so as to shrinkage fit to the outside of the refractory material 2. This method is not at all effective as long as the above-mentioned centering remains possible. Moreover, the reinforcing ring 9 is loosened by heat transfer during the casting process and the effect of the shrinkage fit is lost. Therefore the effect is limited to a short time period during the initial stage of the casting.